This invention relates to heat saving devices which are useful in connection with the flue pipe of a stove, furnace or similar heater.
Such devices have been known for some time, as is evidenced by U.S. Pat. Nos. 1,785,649 and 2,147,658. Inventive activity in this field has been renewed with recent emphasis on energy conservation as is shown by U.S. Pat. No. 4,313,562.
Devices of the type of the present invention function by scavenging the heat carried by exhaust gases and products of combustion, which normally pass through the flue pipe into the atmosphere. The heat accompanying the gases and combustion products would become wasted heat unless transferred to useful air. Useful air thus heated is then circulated into a room or space, adding substantially to the heat provided directly by the basic heater.
It is obviously important that such devices deliver a large volume of heated useful air. This requires the efficient transfer of heat from the exhaust gases and combustion products to useful air. Also necessary is the smooth and relatively unobstructed flow of both useful air and the exhaust gases and products from which heat is extracted for transfer to the useful air. The invention provides a compact and efficient device meeting these objects.
A single open-ended tube forms the inside of a chamber through which the hot exhaust gases and combustion products flow and provides for the smooth and unobstructed flow of a large volume of useful air in efficient heat transfer relationship with the hot exhaust gases and combustion products. The useful air is driven through the tube by a fan. Improved overall efficiency of heat transfer is attained by preheating some of the useful air flowing through the inside tube. This is made possible by a removable shroud positioned around the outside wall of the exhaust gas chamber in spaced relationship to the outside wall, leaving room for useful air to flow between the shroud and the outside wall of the chamber. Air flowing through this space is preheated and then is entrained and mixed with the useful air being blown directly into the inner tube. The resulting whole volume of useful heated air is added to the air directly heated by the stove or furnace. Importantly, means for cleaning residue from both the inside and outside walls of the exhaust gas chamber is included.